In the field of machine tools, it is desireable to have workpiece-holding tools which can be adjusted to conform to the contour of a workpiece. In many types of applications, a workpiece may have an undulating or curved surface. If the jaws of the workpiece-holder present a hard, linear surface, then uneven or unstable pressure may be applied on the workpiece, which could result in deformation or slippage of the workpiece.
Prior approaches to providing an adjustable workpiece holder have certain disadvantages in operation or convenience. In U.S. Pat. No. 1,256,217 to Fieldhouse, U.S. Pat. No. 3,103,353 to Lassy, or U.S. Pat. No. 3,592,461 to Lauriti, an adjustable vise jaw has a plurality of individual plate or block sections in parallel which conform to small variations in the contour of a workpiece by adjustments obtained through one or more rows of loosely-packed rollers or bearings abutting the rear ends of the block sections. However, in such systems, the range of adjustment is severely limited, and the block sections are not securely held in their positions and may slip or assume a different shape upon placement of each workpiece.
In U.S. Pat. No. 1,715,659 to Joksch and U.S. Pat. No. 3,868,102 to Pevar, individual block sections of the jaw are provided with a greater range of adjustment and are more securely held in position by means of a mechanism for applying hydraulic or plastic pressure to the block sections. However, such mechanisms are relatively costly and complex in structure and operation and are not readily retrofitted to existing machine tools.
It is therefore a principal object of the invention to provide an adjustable workpiece-holding system having a plurality of block sections or fingers in parallel, wherein the fingers can be adjusted over a wide range of adjustment yet are held securely in their positions. It is a further object that such a system be inexpensive and simple in structure and operation and can be readily retrofitted to existing machine tools.